It is well known that pultrusion processes are effective continuous processes for producing constant cross-sectional profiles. Conventional pultrusion processes involve drawing a bundle of reinforcing material (e.g., glass filaments or fibers) from a source thereof, wetting the fibers and impregnating them with a preferably thermosettable polymer resin by passing the reinforcing material through a resin bath in an open tank, pulling the resin-wetted and impregnated bundle through a shaping die to align the fiber bundle and to manipulate it to the proper cross-sectional configuration, and curing the resin in a mold while maintaining tension on the filaments. Because the fibers progress completely through the pultrusion process without being cut or chopped, the resulting products have exceptionally high longitudinal strength. Exemplary pultrusion techniques are described in U.S. Pat. Nos. 3,793,108 to Goldsworthy; 4,394,338 to Fuway; 4,445,957 to Harvey; and 5,174,844 to Tong.
Exemplary pultruded articles include tool handles, mine shaft bolts, pipes, tubing, channel, beams, fishing rods and the like. Of particular interest is the manufacture of fiber reinforced rods or bars ("rebar").
Sheet molding compound ("SMC") is a composite comprising fibers, a thermosetting resin (e.g., unsaturated polyester resin), and pigments, fillers, and the like. These components are compounded and processed in sheet form to facilitate subsequent molding of the SMC. SMC is typically compression molded by placing a charge in a matched metal mold and applying pressure and heat with a hydraulic press, which causes the SMC to flow to all areas of the mold. See, Composites, "Sheet Molding Compounds" Engineered Materials Handbook.TM., vol. 1, pp. 157-160 (1987).
Although pultrusion apparatus and apparatus for molding SMC are separately known, it would be desirable to provide an apparatus that effectively combines the pultrusion apparatus and an apparatus for molding SMC. It would be particularly desirable for such apparatus to enable the continuous manufacture of such rebar.
It is, therefore, an object of the invention to provide an apparatus combining a pultrusion apparatus and an apparatus for molding SMC. It is another object of the invention to provide an apparatus for making reinforcing structural rebar comprising a pultruded core of a thermosetting resin and an outer layer of SMC. Other objects, features, and advantages of the invention will be particularly identified below.